nicolas75
i used to have the same problem on my iphone SE,
workaround is to just bluetooth airdrop to ipad and then upload
.,..,,,,
actually my iphone now allows uploading again,

- latest ios + apps
- low data mode on
- javascript on
- request desktop setting
- advanced : webkit feature flag : restore default

or

- general / reset / network settings
My kids explained that Apple pushes a lot of useless crap with each update and as such all your usual settings get confused. Especially now that we get a lot of junk AI modules integrated ....
Resetting : network settings should help,
Beware: though ... one must refill in passwords for known networks again the applicable passwords so note them down first

Or if all else fails ... pop over to Apple store to show the problem and they can toggle the right settings